Various chemicals, such as fertilizers and herbicides, are used in horticulture to manage plant growth by improving the health of desirable plants and killing undesirable weeds. These plant chemicals are typically applied by spraying. However, spraying is non-selective. Spraying herbicides tends to destroy all plant life in the sprayed area. It is often desirable to apply herbicides and other plant chemicals only to certain vegetation, for example to kill weeds but to leave desirable plants unharmed.
The Weed-Killer Applicator disclosed in U.S. Pat. No. 2,979,757 is an apparatus that is capable of selectively applying herbicide to a specific area while minimizing exposure to the surrounding areas. The reservoir described therein consists of a narrow tube for containing weed killer. One end of the tube includes a cap that serves as a fill port. At the other end of the tube, a spring-loaded valve governs the release of herbicide onto a sponge. When the sponge is pressed against a weed plant, the valve is actuated, dispensing a small amount of weed killer onto the sponge, which transfers the weed killer to the weed. Because the reservoir is a narrow tube, it is difficult to fill the reservoir, and spillage is a significant problem. This is particularly true if the chemical to be applied is poisonous, but any spillage constitutes waste and is therefore to be avoided.
Various other similar apparatuses for accomplishing this task are known, most of which are variations on the apparatus described above. For example, the “weed destroyer” of U.S. Pat. No. 2,209,731 omits the sponge but instead utilizes a spring-loaded spike to open a wound in the weed and to dispense chemicals into that wound. U.S. Pat. No. 2,577,687 substitutes a footed rod for the spike. U.S. Pat. No. 3,096,534 retains the sponge but omits the reservoir. U.S. Pat. No. 4,409,755 describes an applicator with an offset head and a wide sponge for wipingly applying liquid herbicide.
What is needed is a portable hand-held apparatus capable of selectively applying herbicide and other plant chemicals to the precise area that needs treatment, so that the plant chemical is applied only to the intended plant with a minimum of exposure to other plants in the surrounding area. Such an apparatus should facilitate the filling of the reservoir with the plant chemicals and should minimize the waste and hazards posed by the spilling of those chemicals, both during filling and in general operation.